By F.W. Karasek, R.E. Clement (University of Waterloo, Waterloo, Ontario, Canada)
By R K Dart (Loughborough University of Technology, UK)
By Bassey J.S. Efiok
By De Levie
By T. Claridge (Dyson Perrins Laboratory, South Parks Road, Oxford OX1 3QY, UK)